Tubes that accumulate after bobbins have been unwound in a textile winding machine and that are conveyed on tube support members having posts on which the tubes are supported must be doffed from the posts before full bobbins are mounted on the posts for conveyance to the spinning machine. Various kinds of equipment have been proposed for this purpose.
Doffers that operate with grippers such as U.S. Pat. No. 4,660,367 have gained widespread acceptance. Such doffers are relatively complicated and do not permit a high throughput capacity. The throughput capacity of such doffers can be improved, by providing a plurality of grippers. For example, in Swiss Patent 424 568 the grippers are moved synchronously with the posts of the bobbins on a spinning machine for a predetermined portion of the path. An apparatus of this kind is also relatively complicated and requires a closely and accurately spaced arrangement of the bobbins.
U.S. Pat. No. 4,674,636 discloses a doffer that doffs the tubes by use of an endless belt and an opposed plate that move against a tube positioned therebetween. It requires actuating devices, so as to be actuated in a synchronous manner tuned to the delivery of the tubes to be doffed. Additionally, U.S. Pat. No. 4,674,636 has a single substantially vertically extending doffing belt as well as a roller. Both the doffing belt and the roller are movable from a retracted position out of engagement with a tube to a tube engaging position. Once again this requires synchronization of the device with the bobbins and also requires a mechanism for moving the components into and out of operating position.
German Patent Document 4024787Cl discloses a device for doffing of tubes having two opposed doffing belts inclined obliquely upward in a wedge-like fashion to grasp the lower ends of tubes and progressively remove them from posts fixed to a main conveyor belt as the conveyor advances. This requires synchronization of the movement of the doffing belts and the posts fixed to the main conveyor.